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Riccardo Balistrerri
science forum beginner
Joined: 19 Apr 2006
Posts: 11
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 Posted: Wed May 24, 2006 12:59 am Post subject:
another air conditioning question
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Hello guys,
I enjoyed reading the conversation about the air conditioning, even if at
some points was a bit too... Anyway, I think I heard that is better to have
the air conditioner run 24/7 for mantainance and cost... is that true of
conventional air conditioners and a work enviromnent where the space is used
for half of the day... (I'm working in Malaysia... hot and humid!)
Thank you,
R. |
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N:dlzc D:aol T:com (dlzc)
science forum Guru
Joined: 25 Mar 2005
Posts: 2835
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| Posted: Wed May 24, 2006 1:25 am Post subject:
Re: another air conditioning question
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Dear ri:
"ri" <riccardo.balistreri@poste.it> wrote in message
news:4473b003$1_1@news.tm.net.my...
| Quote: | Hello guys,
I enjoyed reading the conversation about the air
conditioning, even if at some points was a bit too...
Anyway, I think I heard that is better to have the
air conditioner run 24/7 for mantainance and cost...
is that true of conventional air conditioners and a
work enviromnent where the space is used for half
of the day... (I'm working in Malaysia... hot and
humid!)
|
Unless you sell electricity, replacement units, or service on
existing units, then *of course* it is a good idea to spread this
rumor. ;>)
No it is NOT better to leave the air conditioner running at the
same temperature setpoint 24/7. If the compressor can be started
with a VFD or "soft start", then you will save wear and tear on
that component. A good unit probably already has this feature
(or one that bypasses the expansion valve on startup, or some
such "load limiter"). If the system is well designed and
implemented, and has the proper refrigerant charge, then liquid
ingestion issues are non-existant.
It is not necessary to keep the plant air "cold" off shift.
There are "electronic thermostats" that can alter the temperature
setpoint based on a schedule. This will be probably your best
bet. The plant doesn't have to become supersaturated with
heat/humidity, and then the A/C unit has to climb out of the
hole... Might be good to limit what exhaust fans can run when
the A/C is off also, as they will provide high loads.
Lastly, the air filters can/will provide a negative air pressure
in the ducting between the filter elements and the fan, and this
too can carry a penalty if the fan is left running continuously.
David A. Smith |
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Chris W
science forum beginner
Joined: 19 Jun 2005
Posts: 20
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| Posted: Wed May 24, 2006 6:28 am Post subject:
Re: another air conditioning question
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N:dlzc D:aol T:com (dlzc) wrote:
| Quote: | It is not necessary to keep the plant air "cold" off shift.
There are "electronic thermostats" that can alter the temperature
setpoint based on a schedule. This will be probably your best
bet. The plant doesn't have to become supersaturated with
heat/humidity, and then the A/C unit has to climb out of the
hole...
|
This brings up another question I had. Wouldn't setting the thermostat
to a low temperature at say around 3AM, so it slowly cooled the building
off to a pretty low temperature help? That way it wouldn't require as
much energy to keep it cool during the day? Kind of like letting your
car build up speed going down the mountain and then slowly bleeding it
off as you climb up the next. Would this be efficient? My guess is
that it may require too low of a setting in the mornings, or too high of
a setting in the afternoon, to be comfortable, if it is going to have a
significant effect.
--
Chris W
KE5GIX
Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
http://thewishzone.com |
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N:dlzc D:aol T:com (dlzc)
science forum Guru
Joined: 25 Mar 2005
Posts: 2835
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| Posted: Wed May 24, 2006 1:18 pm Post subject:
Re: another air conditioning question
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Dear Chris W:
"Chris W" <1qazse4@cox.net> wrote in message
news:K2Tcg.50727$9c6.36725@dukeread11...
| Quote: | N:dlzc D:aol T:com (dlzc) wrote:
It is not necessary to keep the plant air "cold" off
shift. There are "electronic thermostats" that can
alter the temperature setpoint based on a
schedule. This will be probably your best bet. The
plant doesn't have to become supersaturated with
heat/humidity, and then the A/C unit has to climb
out of the hole...
This brings up another question I had. Wouldn't
setting the thermostat to a low temperature at say
around 3AM, so it slowly cooled the building off to
a pretty low temperature help?
|
Only if the unit were so undersized that it couldn't handle the
daytime load.
| Quote: | That way it wouldn't require as much energy to
keep it cool during the day? Kind of like letting
your car build up speed going down the mountain
and then slowly bleeding it off as you climb up the
next.
|
You could "store the cold" in a reservoir, much as is done in
passive cooling systems. Then add heat to the reservoir during
the day. But you would need really good insulation on the
reservoir...
| Quote: | Would this be efficient? My guess is that it may
require too low of a setting in the mornings, or too
high of a setting in the afternoon, to be
comfortable, if it is going to have a significant effect.
|
It would not be efficient, since A/C unit efficiency is really
"tuned" to a particular outside/inside temperature gradient.
Also, the colder you drop the internal temp, the higher the
ambient heat transfer into your building. No it is most
efficient to have the "road ise to meet your feet", and the
building gets to temp just as employees arrive.
David A. Smith |
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YouGoFirst
science forum beginner
Joined: 13 Jul 2005
Posts: 47
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| Posted: Wed May 24, 2006 4:59 pm Post subject:
Re: another air conditioning question
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Assuming that the Air Conditioning is for that room only and the room is
used at a set time every day, you would be best off using a programmable
thermostat. With the thermostat you can set it up to turn on about 1 hour
before people begin to work, and shut off when the room is no longer being
used.
You may also want to consider connecting dehumidifiers to your HVAC system.
That way you remove more humidity than the AC unit alone. Without the
humidity people will be able to cool down in a more natural way.
"ri" <riccardo.balistreri@poste.it> wrote in message
news:4473b003$1_1@news.tm.net.my...
| Quote: | Hello guys,
I enjoyed reading the conversation about the air conditioning, even if at
some points was a bit too... Anyway, I think I heard that is better to
have the air conditioner run 24/7 for mantainance and cost... is that true
of conventional air conditioners and a work enviromnent where the space is
used for half of the day... (I'm working in Malaysia... hot and humid!)
Thank you,
R.
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Harry Andreas
science forum beginner
Joined: 17 Aug 2005
Posts: 22
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| Posted: Wed May 24, 2006 5:29 pm Post subject:
Re: another air conditioning question
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In article <K2Tcg.50727$9c6.36725@dukeread11>, Chris W <1qazse4@cox.net> wrote:
| Quote: | N:dlzc D:aol T:com (dlzc) wrote:
It is not necessary to keep the plant air "cold" off shift.
There are "electronic thermostats" that can alter the temperature
setpoint based on a schedule. This will be probably your best
bet. The plant doesn't have to become supersaturated with
heat/humidity, and then the A/C unit has to climb out of the
hole...
This brings up another question I had. Wouldn't setting the thermostat
to a low temperature at say around 3AM, so it slowly cooled the building
off to a pretty low temperature help? That way it wouldn't require as
much energy to keep it cool during the day? Kind of like letting your
car build up speed going down the mountain and then slowly bleeding it
off as you climb up the next. Would this be efficient? My guess is
that it may require too low of a setting in the mornings, or too high of
a setting in the afternoon, to be comfortable, if it is going to have a
significant effect.
|
Here at my job in SoCal the company does this.
During the summer months they run the airco hard all night when power
is cheap. It's cold as hell in the morning. They shut if off for the peak
hours and the building slowly warms up.
Saves money and saves brownouts, but you look funny wearing a parka
in to work when it's 85F at 8AM.
--
Harry Andreas
Engineering raconteur |
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